1. Field of the Invention
This invention relates to a tire building drum for deforming tire constitutional members in an approximately toroidal form to build a green tire.
2. Description of Related Art
As a conventional tire building drum, as shown in FIG. 6, there is known a drum comprising a main drum shaft 11, a pair of movable bodies 12 movably supported by the main drum shaft 11 in an axial direction, plural bead lock segments 13 movably supported by each of the movable bodies 12 in a radial direction, a piston 16 as an enlarging-contracting means movably housed in the movable body 12 in the axial direction and moving outward in the axial direction so as to synchronously move the bead lock segments 13 along a slant face 15 in the radial direction and enlarge or contract them when a high pressure fluid is fed to a fluid chamber 14 formed together with the movable body 12, and a seal member 17 sealing a space among the movable body 12, bead lock segments 13 and a tire constitutional member K when the tire constitutional member K is supported by the bead lock members 13 enlarged by the piston 16 from an inside in the radial direction.
The seal member comprises a cylindrical portion 17a covering a radially outer end face of the bead lock segment 13 and a width-wide elongated portion 17b extending inward from an axially outer end of the cylindrical portion 17a in the radial direction while closing to an axially outer face of the bead lock segment 13. The elongated portion 17b slidably contacts with the movable body 12 when it moves in the radial direction together with the bead lock segment 13.
In such a conventional tire building drum, however, since the elongated portion 17b of the seal member 17 extending in the radial direction is wider in the width, there is a problem that when the bead lock segments 13 move outward in the radial direction while elongating the seal member 17, they are subjected to a large resistance and hence an ability as an apparatus (speed) lowers. And also, the elongated portion 17b of the seal member 17 generates a large frictional resistance due to the slidable contacting with the movable body 12 when the bead lock segments 13 move outward in the radial direction as mentioned above, so that the ability as the apparatus further lowers.
It is, therefore, an object of the invention to provide a tire building drum developing a higher ability by mitigating a load fed by the enlarging-contracting means.
According to the invention, there is the provision of in a tire building drum comprising a main drum shaft, a pair of movable bodies movably supported by the main drum shaft in an axial direction, approaching-separating means for moving these movable bodies in opposite directions so as to approach or separate them, plural bead lock segments movably supported by each of the movable bodies in a radial direction, enlarging-contracting means for synchronously moving these bead lock segments in the radial direction so as to enlarge or contract them, a seal member sealing a space among the movable body, bead lock segments and a tire constitutional member when the tire constitutional member is supported by the bead lock segments enlarged by the enlarging-contracting means from an inside in the radial direction, a hollow cylindrical body movably fitted onto an outside of the movable body in the axial direction and plural turnup fingers each rotatably connected at its base end part to an axially outer end portion of the hollow cylindrical body and arranged so as to extend substantially inward in the axial direction and separate away in a circumferential direction, an improvement wherein the seal member comprises an inner elongated portion extending inward from the base end part airtightly fixed to the movable body axially located at the inside of the bead lock segment in the axial direction and an outer elongated portion extending outward from an inner end of the inner elongated portion in the axial direction and covering radially outer portions of the bead lock segments at its top end part.
As mentioned above, since the seal member comprises the inner elongated portion extending inward from the base end part in the axial direction and the outer elongated portion extending outward from the inner end of the inner elongated portion in the axial direction, when the top end part of the outer elongated portion is enlarged by moving the bead lock segments outward in the radial direction, the inner and outer elongated portions are merely deformed in V-shaped form at section and a large resistance is not caused to the bead lock segment and hence a load applied to the enlarging-contracting means can be mitigated to increase the ability as an apparatus (speed). And also, the seal member does not frictionally contact with the movable body when the bead lock segments move in the radial direction, so that the load applied to the enlarging-contracting means can be further mitigated to more enhance the ability as the apparatus.
In a preferable embodiment of the invention, an outer face of the top end part of the outer elongated portion is subjected to an adhesion-preventing treatment for preventing the adhesion to the tire constitutional member. Thus, when the bead lock segments move in the radial direction, the top end part of the seal member (the outer elongated portion) is easily peeled off from the tire constitutional member (green tire), whereby the resistance is decreased and the turning-over of the seal member is prevented.
In another preferable embodiment of the invention, a stopper body restricting an inner moving quantity of the hollow cylindrical body is interposed between an axially outer part of the movable body and the hollow cylindrical body and a fixing body for fixing the stopper body while adjusting an axial position thereof is arranged on an axially outer end of the movable body. Thus, a swinging quantity of the turnup fingers (turnup height of the tire constitutional member) can easily be adjusted from exterior without decomposing the drum.
In the other preferable embodiment of the invention, the enlarging-contracting means comprises a piston movably housed in a cylinder chamber in the axial direction and plural links connecting the piston to the bead lock segments so as to enlarge or contract the bead lock segments by alternately feeding a fluid into the cylinder chamber located at both sides of the piston. Thus, the bead lock segments can be strongly moved at a high speed in the radial direction to improve the operation efficiency.
In a further preferable embodiment of the invention, a finger receiver projecting outward in the axial direction is arranged at the outer end portion of the bead lock segment in the radial direction so as to place the top end part of the turnup finger on the finger receiver. Thus, the top end part of the turnup fiber moves together with the bead lock segments outward in the radial direction, whereby the occurrence of wrinkles and the flowing of air are prevented in a turnup portion of the tire constitutional member.
In a still further preferable embodiment of the invention, each of the bead lock segments, turnup fingers and seal member is exchangeable so as to exchange them in accordance with a given tire size in the building of tires having various sizes. Thus, tires having different sizes can easily be built without exchanging the drum.